Question: The drama club sold bags of candy and cookies to raise money for the spring show. Bags of candy cost $$7.50$, and bags of cookies cost $$4.00$, and sales equaled $$70.00$ in total. There were $6$ more bags of cookies than candy sold. Find the number of bags of candy and cookies sold by the drama club.
Explanation: Let $x$ equal the number of bags of candy and $y$ equal the number of bags of cookies. The system of equations is then: ${7.5x+4y = 70}$ ${y = x+6}$ Since we already have solved for $y$ in terms of $x$ , we can use substitution to solve for $x$ and $y$ Substitute ${x+6}$ for $y$ in the first equation. ${7.5x + 4}{(x+6)}{= 70}$ Simplify and solve for $x$ $ 7.5x+4x + 24 = 70 $ $ 11.5x+24 = 70 $ $ 11.5x = 46 $ $ x = \dfrac{46}{11.5} $ ${x = 4}$ Now that you know ${x = 4}$ , plug it back into $ {y = x+6}$ to find $y$ ${y = }{(4)}{ + 6}$ ${y = 10}$ You can also plug ${x = 4}$ into $ {7.5x+4y = 70}$ and get the same answer for $y$ ${7.5}{(4)}{ + 4y = 70}$ ${y = 10}$ $4$ bags of candy and $10$ bags of cookies were sold.